1. Field of the Invention
The present invention relates to the art of electrical connectors, and more particularly to a land grid array (LGA) connector assembly provided for mechanically and electrically connecting a land grid array (LGA) chip to a printed circuit board (PCB).
2. Description of the Prior Art
Land grid array (LGA) electrical connectors are widely used in the connector industry for electrically connecting LGA chips to printed circuit boards (PCBs) in personal computers (PCs). Conventionally, an LGA connector mainly comprises an insulative housing, a multiplicity of terminals received therein, a load plate and a cam lever pivotably mounted on two opposite sides of the housing. The housing defines a multiplicity of terminal passageways in a rectangular array, for interferentially receiving corresponding terminals. Due to the very high density of leads arranged on an LGA chip, the LGA chip needs to be precisely seated on the LGA connector. Thus it is difficult to ensure reliable signal transmission between the terminals and the LGA chip.
Referring to FIGS. 4, 5 and 6, a conventional land grid array connector assembly 8 comprises an insulative housing 82, a plurality of terminals 81 received in corresponding passageways 824 of the housing 82, a metal stiffener 84 partly covering and reinforcing the housing 82, a metal clip 88 pivotably attached to an end of the stiffener 84, and a cam lever 86 pivotably mounted to an opposite end of the stiffener 84 for engaging with the cam lever 86. The housing 82 defines four sidewalls and a central cavity disposed between the sidewalls. The central cavity is used for receiving a land grid array (LGA) chip (not shown) therein. A pair of spaced protrusions 822 extends arcuately from an outside of one sidewall. A distal end of the terminal 81 is formed outward from a top surface of the central cavity, for being pressed to engage a corresponding lead of the LGA chip. The clip 88 comprises two first opposite sides 880 and two second opposite sides 881 adjacent to the first sides 880 respectively. A pair of pressing portions 883 each is provided at respective middles of the first sides 880, for pressing the LGA chip electrically engaging with the terminals 81. An engaging portion 884 is extended arcuately from one second side 881, a pair of spaced securing portions 882 extended arcuately from the other second side 881 and pivotably received in corresponding slots 842 of the stiffener 84.
When the LGA chip engages with the connector assembly 8, the clip 88 is rotated upward, the LGA chip is placed in the central cavity of the housing 82. The clip 88 is rotated from a vertical portion to a horizontal portion to make the two opposite first sides 880 of the clip 88 attach on corresponding sides of the LGA chip. The cam lever 86 is rotated to the housing 82 to drive the clip 88 to gradually approach the housing 82 until the pressing portions 881 of the first sides 880 press the LGA chip downwardly to make the leads of the LGA chip contact with the distal ends of the terminals 81. As a result, the mechanical and electrical engagement between the terminals 81 and corresponding leads (not shown) of the LGA chip is attained.
However, when the cam lever 86 is rotated toward the housing 82, a user applies force on an operating portion of the cam lever 86 (not labeled). The force will drive an actuating portion (not labeled) of the cam lever 86 to touch and pressing on the engagement portion 884 of the clip 88 for locking the clip 88. This force is typically along an inclined direction, as indicated by arrow F in FIG. 5. Force F comprises the component force Fx acting along a direction parallel to the housing 82, and the component force Fy acting perpendicularly downwardly relative to force Fx. The effect of force Fx is to make the securing portions 882 of the clip 88 move toward the sidewall 820 of the housing 82 and drive the LGA chip to move toward the sidewall 820 (best seen in FIG. 6). As a result, it is prone to destroy the sidewall 820.
In addition, because the pressing portion 883 is formed in the middle portion of the clip 88, when the pressing portions 883 of the clip 88 press on the LGA chip, only one point of the clip 88 attaches on the LGA chip. The pressing force applied on the LGA chip will generate friction between the LGA chip and the housing 82. The friction is prone to make the LGA chip move relative to the housing 82 in vertical direction and spaces are formed between the leads of the LGA chip and the terminals 81. As a result, the reliability of the mechanical and electrical engagement between the leads of the LGA chip and the terminals 81 is decreased. If this happens, the LGA chip can not be secured between the sidewalls of the housing 82 reliably, and some terminals 81 are prone not to fully engage the corresponding leads of the LGA chip. Uniform engagement between the terminals 81 and the corresponding leads of the LGA chip is destroyed, and even open electrical circuits are liable to establish therebetween. Thus, the reliability of the mechanical and electrical engagement between the terminals 81 and the corresponding leads of the LGA chip is decreased.
Thus, there is a need to provide a new land grid connector assembly that overcomes the above-mentioned problems.